The present application is related to the co-pending U.S. patent application Ser. No. 08,000,072 entitled "Apparatus and Method for Storing and Printing Image Data", filed Jan. 4, 1993 (Attorney Docket No. D/92498).
The present invention relates generally to a technique for printing a stream of image data written in a printer page description language and more specifically to an image filtering arrangement which selectively removes one or more images from the stream of image data to thereby form a modified stream of image data.
Network printing systems are becoming prevalent in office settings where extensive document processing is performed. In one example of such network printing systems, a client at an input, such as a workstation, sends electronic documents that comprise a job over a local area network (LAN) to one of the printers selected for printing of the job. In particular, LANs provide a means by which users running dedicated processors are able to share resources such as printers, file servers and scanners. Integration of shared resources has been a problem addressed by LAN managers. LAN managers have made different network protocols transparent to devices running different network protocols. LANs also have a variety of print drivers emitting different page description languages (PDLs), which are directed to specific print devices.
In the exemplary network printing system, image data is transmitted to an electronic printing system, such as a network DocuTech.RTM. electronic printer manufactured by Xerox.RTM. Corporation, in the form of a stream of image data expressed in terms of the PDL. The PDL stream can include, among other things, an image, such as a bitmap, or a reference to one or more images existing outside of the PDL stream. Preferably, as discussed in the following patent application, the pertinent portions of which are incorporated herein, a decomposer, with one or more processors and suitable software, is employed to "take apart" an input document so that the PDL is "parsed" into various image related components with a preparser.
Patent application Ser. No. 07/898,761 Entitled: Apparatus and Method for Multi-Stage/Multi-Process Decomposing Filed: Jun. 12, 1992
As discussed in the above-indicated reference, the decomposer executes the PDL to generate imaging primitives. In doing this, the decomposer, for example uses an arrangement for parsing the PDL into various image related components. The types of operations required to generate imaging primitives include, among others, binding fonts with requested fonts, any image processing on pictorial information, and/or converting line art/graphics (including bitmaps) to lower level primitives.
As disclosed in the above-discussed reference, the decomposer of the exemplary network printing network is designed to receive only one job file at a time. While the system can store a plurality of job files, in anticipation of parsing them, such storage can result in less than desirable machine output, or, more specifically, in reduced printing speeds. That is, the amount of image data contained in a given job file can be relatively large, if not immense, so that storing the job file out, rather than transmitting it directly from the network input to the parsing arrangement, can result in loss of time since, due to the amount of image data in the job file, a significant delay inevitably occurs when the job file is retrieved from storage for decomposing.
Additionally, due to the size of various images in the job file, and the finite resources of the decomposer, a significant amount of time can be expended in parsing the images of the PDL stream. Delays generated by relatively slow parsing can be compounded in a system where multiple jobs are queued up for decomposing. For example, in a situation where n jobs are queued up for decomposing, the time that it takes for the decomposer to finally get to the nth job will be affected by the amount of time that it takes to parse each of the n-1 job files which is ahead of the nth job file in the queue.
It would be desirable to provide an intelligent spooling arrangement which maximizes throughput of the printing system.